Refinement of asbestos



Aug. 10, 1954 J NOVAK 2,685,825

REFINEMENT 0F ASBESTOS Filed May 28, 1949 2 Sheets-Sheet l llllll. IIIIIJ 0, 1954 l. J. NOVAK 2,685,825

REFINEMENT 0F ASBESTOS 2 Sheets-Sheet 2 Filed May 28, 1949 I Ear/ al on 12W? LIL/fowl;

amount of detergent being in excess of that adsorbed on the asbestos and suflicient to form and preserve or maintain the dispersion in a stable manner. Typical examples of such dispersing agents are Aerosol OT (dioctyl sodium sulfosuccinate) sodium oleate, and others more fully particularized in my said co-pending application. Treatment of the asbestos in this manner causes separation, individualization, dissemination and unclotting of the asbestos fibers, and converts them to single fibers or fascicular fiber bundles instead of the predominantly clotted and tangled multiple fiber groups known to prior wet or dry asbestos practice. The fibers in such dispersion are in a lubricated, slippery, relatively slidable condition and composed predominantly of ashestos fibers of unit size, or fibro-colloidal diameter, that is, of a diameter of from about 200 to about 500 angstrom units.

The following is one example of a typical method for producing an asbestos dispersion in dilute condition suitable for subsequent refining: To 1000 gallons of water were added 312 pounds of 25% Aerosol OT in water and dissolved. Then 212 pounds of Canadian 3R spinning grade chrysotile asbestos were added, which on stirring produced a smooth slurry of 2%% asbestos concentration. This was further diluted by adding water slowly in the volume proportion of 9 parts of the 2%;% slurry to 47 parts water. This produced a dispersion on mixing for four hours of the character previously described.

Treatment of the asbestos in this manner not only dispersed and individualized the asbestos .fibers, but freed previously occluded and entangled non-fibrous associated impurities of the character previously described. By taking advantage of the jellylike water-holding characteristics of the opened mass, it may be strained through fine slotted screen plates such as are used in paper and pulp screening as illustrated in Fig. 1. The mass will even pass through a wire screen, say 10 to 20 mesh, but tends to tangle badly on such screen because two ends of the same fiber may pass through two different openings in the screen and thereby hang on the screen.

Thus, when refining dilute dispersions, such as of 0.1% to 1.0% by weight of asbestos, I have found that the diaphragm or flat screen type of apparatus of Fig. '1 is highly effective in not only removing impurities of a non-fibrous nature, but also larger spicules of picrolite, and clots or bundles of oversize or inadequately opened fibrous material.

Referring to Fig. 1 of the drawings, a asbestos dispersion, prepared in accordance with the foregoing example, was supplied from the stock chest I through line I l and valve [2 to the flat bed screening device generally indicated as IS. The device !3 is a conventional type of papermaking screen comprising a fiat bed of brass screen plates I 4 with fine slots 9 cut vertically through the brass plates. These slots may be as narrow as from about .010 to about .015 inch and having a length of about 4 inches. These brass plates are mounted within an upwardly open chamber I5 which receives the dispersion from the stock chest ID, the refined dispersion passing through the slots in the screen to the lower chamber portion [6 and is delivered therefrom through the passage I! to the flow box l8 and then transferred from the latter by means of the conduit I 9, valve 20 and pump 2! to the screened stock chest 22. A vibrating flexible diaphragm 23 at the bottom of the closed chamber section [6 actuated by the eccentrically mounted plunger 24 forces the slurry up and down through the slots in the screen plates, thereby keeping them open, screening being accomplished by a combination of gravity flow and suction. The tailings are removed from one end of the screen plate [4, either intermittently or continuously, for example, by the diagrammatically indicated reciprocal scraper means 25. These tailings, as previously indicated, comprise large spicules of unopened bits of harsh yellow fiber (picrolite), grains of magnetite, rock, clots of fiber, pieces of wood, etc., such impurities being found in comparatively large proportion even in commercially opened fiber for yarn making. Other devices embodying slotted screen plates may be used, as, for example, the Jonsson screen which operates with the screen plates flooded with the slurry and removes the tailings by a controlled vibratory motion which carries them up an inclined screen plate surface into an exit trough.

For asbestos dispersions of the foregoing nature, that is to say below 1% asbestos concentration, I may, as a non-fully equivalent alternative, employ a centrifugal refiner, as diagrammatically illustrated in Fig. '7, and which is of the type used in the paper industry, such as Erkensator or Bird Centrifiner, which operate on the principle of removing tailings from the outer portion of the centrifuged pulp and the refined slurries from the center portion of the centrifuged pulp. This, as illustrated in Fig. '7, such device comprises a rotatably mounted cylinder 26 supplied at one end through its axial conduit 21, the refined pulp being discharged from the axial conduit 28 and line 29. The heavier tailings are discharged from adjacent the periphery of the cylinder 26 through the outlet 30 and to the fixed chamber 3|, wherefrom they are discharged from the outlet 32 of the latter. Another device in which the centrifugal effect is obtained by causing the slurry to swirl violently in a rifled tube with an accompanying pressure drop is also eifective. This is the Dirtec made by Bird Machine Co.

For the refining of heavier slurries or dispersions, for example 30% and upwards asbestos content, it is possible to use a variation of a strainer of the type used for removing oversize particles from rubber compounds, particularly where the compounds are to be later extruded. This variation is illustrated in Fig. 3 and comprises a hopper 33 for reception of the stock to be strained and an elongated cylindrical chamber 34 enclosing the pressure feed screw 35 driven through gear 36. In place of a heavy wirescreen backed up by a perforated plate employed in rubber practice, I employ a heavy plate 31 provided with fine longitudinal slots therein of a construction similar to that of the slotted plate 14, illustrated in Figs. 1 and 2 employed in papermakers screen for screening pulp. The screw 35 in my strainer is longer and larger than that conventionally employed in rubber strainer practice because of the lower friction of a plastic asbestos dispersion of the indicated concentration, than that of rubber compounds. Although not shown, means may be provided for rapid removal of the slotted plate for cleaning.

For more fluid dispersions, say from 10 to 30% asbestos concentration, I may employ an apparatus such as that shown in Fig. 5 comprising a cylindrical chamber 38 provided with a hydraulic arm 39 and a slotted screen plate 40, similar to that of the plate 31 of Figs. 3 and 4. By this means a semi-plastic mass of such concentration may be effectively forced through the screen plate 40 and suitably refined thereby.

For asbestos dispersions below concentration, I may suitably employ a centrifugal baskettype refiner, as illustrated in Fig, 6. This comprises an outer cylindrical chamber 41 containing a basket 42 mounted for rotation therein by means of the shaft 43 and pulley 44. The peripheral wall of this basket 42 is provided with elongated narrow slots 45, similar to the slotted plates previously described. The dispersed asbestos to be refined is supplied from the conduit 46 to the interior of the rotatable basket 42 and then the refined material passes through the slots 45 into the outer chamber 4| and is discharged therefrom through the conduit 41. The interior surface of the basket 42 is kept free of tailings by means of the fixed scraper 48. In general, the slotted screens serve to remove spicules and clots and grains larger than the openings, although some finer impurities entangled in the tailings are also removed; the centrifugal separators remove substances of different gravity, particularly magnetite, sand, and dense unopened bits of fibrous rock.

The asbestos dispersion which free, or substantially free, of foreign materials or unopened aggregates of asbestos, and thus, being of a refined nature, is suitable for fabrication into many useful products, such as generally described in my aforementioned co-pending application. For example, the dilute slurries may be sheeted out on a paper-making machine; thin webs thereof may be converted into smooth, level, fine yarns in accordance with the co-pending application of Novak-Palm, Serial No. 90,238, filed April 28, 1948, now Patent No. 2,578,941, and plastic or semi-plastic slurries, either refined as such as hereinbefore described, or concentrated from the highly dilute slurries, may be employed for the manufacture of extruded products, such as, for example, extrusion about wires in acordance with my co-pending application, Serial No. 85,187, filed April 2, 1949.

Although I have shown and described several m:

devices and arrangements of apparatus for refining my asbestos dispersions, it will be understood that other related and modified arrangements of apparatus may be employed within the scope of my invention.

I claim as my'invention:

The method of refining chrysotile asbestos which comprises reducing chrysotile asbestos agglomerates of spinning grade length fibers to the form of a stable, aqueous, individualized, fibrocolloidal dispersion, by mixing with said agglomerates an aqueous liquid containing organic surface active detergent adsorbable on the asbestos and capable of forming an alkaline gelatinous dispersion therewith, and segregating from said colloidal dispersion oversize and relatively different density particle material by subjecting said dispersion to slotted screening and centrifugal separation.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 660,764 Welch Oct. 30, 1900 1,091,899 Shartle Mar. 31, 1914 1,684,365 Dolbear Sept. 11, 1928 1,741,869 Mett Dec. 31, 1929 1,750,725 Miller Mar. 18, 1930 1,885,113 Jenkins Nov. 1, 1932 1,887,726 Weber Nov. 15, 1932 1,899,106 Richter et al Feb. 28, 1933 1,907,616 Tucker May 9, 1933 2,060,685 Murphy Nov. 10, 1936 2,068,219 Badollet Jan. 19, 1937 2,217,005 Clapp Oct. 8, 1940 2,220,386 Badollet Nov. 5, 1940 2,225,100 Clapp Dec. 17, 1940 2,265,936 Co-wles Dec. 9, 1941 2,312,545 Haug Mar. 2, 1943 2,335,373 Woodward Nov. 30, 1943 2,338,904 Cowles -1 Jan. 11, 1944 2,352,968 Orton July 4, 1944 2,376,687 Goldstein et a1 May 22, 1945 2,376,688 Goldstein et a1 May 22, 1945 2,386,713 Pharo Oct. 9, 1945 2,419,155 Orton, Jr Apr. 15, 1947 2,460,938 Koehne Feb. 8, 1949 2,626,213 Novak Jan. 20, 1953 FOREIGN PATENTS Number Country Date 159,284 Germany Mar. 17, 1905 13,412 Australia Feb. 19, 1929 of 1928 

